1. Field of the Invention
The invention relates to a support frame device for connecting a seat portion to an upright post, more particularly to a support frame device that is convenient to assemble and that has good structural strength.
2. Description of the Related Art
A conventional office chair generally includes a swivel base with an upright post connected to a seat portion so as to permit swiveling and easy removal thereof. The upright post is connected to the seat portion via a support frame device. For purposes of height adjustment, an upper end of the upright post is provided with a retractable pneumatic rod that extends into the support frame device. As the load borne by the chair is transferred to the upright post via the support frame device, there is a concentration of stress on the support frame device. In order to have sufficient supporting strength, the support frame device has to be formed from metal materials of preferred strength.
FIG. 1 shows a conventional support frame device 1, which includes a base mounting plate 11 adapted to be mounted beneath a seat portion (not shown), and a spacer plate 12 disposed on a bottom portion of the base mounting plate 11 and formed with a through hole 121. Both of the base mounting plate 11 and the spacer plate 12 are formed from a metal material. A post mounting member 122 has a periphery welded to a bottom portion of the spacer plate 12, and is formed with an upwardly tapered hollow stem 123 that is aligned with the through hole 121. An upright post 14 of a swivel base (not shown) is inserted via the hollow stem 123 through the through hole 121 to be retained in the hollow stem 123 and the spacer plate 12. The post mounting member 122 is formed from a metal material of preferred strength in order to enhance the structural strength of the device 1. One problem with the conventional support frame device 1 resides in that the process of welding the post mounting member 122 to the spacer plate 12 is troublesome. In addition, the welded parts may become brittle due to carbonization of the metal material thereof, and may consequently break upon prolonged application of shear forces generated by loads borne thereby.
FIG. 2 shows a conventional support frame device 2 including a base mounting plate 21 that has an intermediate portion punched to form a substantially U-shaped spacer plate 22 with an integrally formed downwardly extending hollow stem 23 for retaining therein an upright post 24. Although the need to weld the hollow stem 23 to the spacer plate 22 and the associated problem are eliminated, the entire support frame device 2 has to be made of a metal material of preferred strength, which results in increased material costs.
FIG. 3 shows a conventional support frame device 3 that has a spacer plate 32 pivotally mounted to a bottom portion of a base mounting plate 31, the spacer plate 32 having a bottom portion formed with an opening for receiving a hollow stem portion 33 of a post mounting member. The post mounting member has a square base 331 secured to the bottom portion of the spacer plate 32 through the use of rivets 332 at the four corners. In this construction, although it is only necessary to have the post mounting member to be formed from a metal material of a preferred strength or greater thickness, the riveting process is troublesome.
Therefore, the object of the present invention is to provide a support frame device for connecting a seat portion to an upright post, which eliminates the aforesaid drawbacks.
Accordingly, a support frame device for connecting a seat portion to an upright post of the present invention includes an anchoring member, an anchored member, a securing member, an annular stiffening member, and a connecting member. The anchoring member includes a base mounting plate with first right and left sides opposite to each other in a transverse direction and adapted to be mounted beneath the seat portion. Right and left anchoring plates are integrally formed with, and respectively extend from the first right and left sides of the base mounting plate in an axial direction and away from the seat portion. The anchored member includes a spacer plate with second right and left sides opposite to each other in the transverse direction, and upper and lower walls opposite to each other in the axial direction. The upper and lower walls include upper and lower peripheral edge portions, respectively, which cooperate to confine a mounting bore that defines an axis parallel to the axial direction. Right and left anchored plates are integrally formed with, and respectively extend from the second right and left sides of the spacer plate in the axial direction and away from the lower wall. The securing member is disposed to secure the right and left anchored plates respectively to the right and left anchoring plates such that the upper wall of the spacer plate cooperates with the base mounting plate to define an accommodation space in the axial direction. The stiffening member has an annular abutment end disposed to abut against the lower peripheral edge portion, and an annular seat end opposite to the annular abutment end and distal to the lower peripheral edge portion. The annular seat end cooperates with the annular abutment end to define an axial passage adapted to allow the upper end of the upright post to pass through. The connecting member includes a hollow stem having lower and upper annular ends opposite to each other in the axial direction, and an inner annular wall extending from the lower annular end to the upper annular end to confine an axial through hole adapted to permit the upper end of the upright post to move retainingly therein relative to the inner annular wall in the axial direction. A flange portion is integrally formed with, and extends from the upper annular end in radial directions. The flange portion abuts against the upper peripheral edge portion when the hollow stem is inserted into the mounting bore with the lower annular end thereof extended through the axial passage and downwardly of the annular seat end. The lower annular end is malleated to form an outwardly and radially extending flared portion that abuts against the annular seat end.